[unreadable] The primary goal of this project is determination of the value of positron emission tomography employing the radiopharmaceutical C-11 acetate (AC-PET) in patients with medium- and high-risk prostate cancer who are candidates for treatment with curative intent by radical prostatectomy or radiation therapy because the standard clinical and imaging evaluation was negative for tumor spread beyond the prostate. The following specific aims will be pursued: 1. Determine the role of AC-PET in changing initial patient management; 2. Determine the value of AC-PET in predicting recurrence; 3. Assess the performance of AC-PET for detection of lymph nodes by comparison with biopsy. Study Design: The study includes a total of 285 patients in two groups who are scheduled for treatment with curative intent, both of whom will undergo AC-PET imaging prior to treatment. For the surgery group, if the PET examination is negative for disease outside the prostate gland, the treatment will proceed and the patient will be followed for evidence of recurrence. If the PET examination is positive, the referring physician will be encouraged to undertake confirmatory studies, which may lead to a change in therapy. All patients in the radiation therapy group will undergo the standard treatment, and they will then be followed for evidence of recurrence. The lymph node biopsy results in the surgery patients will be correlated with the PET findings to compute the positive and negative predictive values of AC-PET. Anticipated Results: AC-PET will lead to cancellation of radical prostatectomy in at least 10% of the surgical patients. It is also expected that AC-PET will significantly improve the prediction of recurrence compared with conventional methods based on clinical stage, PSA and Gleason score. The predictive value of AC-PET should be high when correlated with the pathological data. Health Relevance: If this project is successful, it will have a significant impact on the management of patients with moderate- and high-risk prostate cancer who are candidates for curative treatment. In some of these patients, a positive PET scan will lead to cancellation of planned surgery, sparing these men the morbidity of radical surgery while permitting some of them to receive more appropriate hormonal treatment. PET may also contribute significant prognostic information that may affect the decision to administer early adjuvant therapy to delay or prevent recurrence. [unreadable] [unreadable]